1. Field of the Invention
This invention relates to a process for separating a meta-substituted benzene or 1,3,5-substituted benzene from a substituted benzene isomer mixture containing a meta-substituted benzene or 1,3,5-substituted benzene nuclearly substituted with a methyl, ethyl or hydroxyl group or a halogen atom.
2. Description of the Prior Art
m-Chlrotoluene among chlorotoluene (hereinafter referred to as "CT") isomers, m-dichlorotoluene among dichlorotoluene (hereinafter referred to as "DCB") isomers and 3,5-xylenol among xylenol (hereinafter referred to "XYOH") isomers are important as intermediate substances for agricultural chemicals and medicines, and m-diethylbenzene among diethylbenzene (hereinafter referred to as "DEB") isomers is valuable as a desorbent or an intermediate substance for a crosslinking agent. However, considerable difficulties are encountered in separation of these compounds by distillation because their boiling points are very close to those of their isomers.
If there is available an adsorbent capable of adsorbing a specific isomer selectively, separation of isomers will be accomplished at a high efficiency economically advantageously. An isomer capable of being strongly adsorbed in the adsorbent is selectively adsorbed in the adsorbent to be thereby separated as an extract component, and an isomer capable of being weakly adsorbed in the adsorbent is weakly adsorbed in the adsorbent to be thereby separated as a raffinate component. Thus, the isomer mixture is separated into the respective isomers.
U.S. Pat. No. 4,356,331 discloses a process in which a para-isomer is selectively adsorbed and separated from an alkyl phenol isomer mixture by using a zeolite of the Y type.
Furthermore, European Patent Application No. 81303609.2 discloses a process in which a para-isomer is selectively adsorbed and separated from a halogenated toluene isomer mixture by using a zeolite of the Y type.
However, these prior art references do not teach separation and recovery of meta-isomers.
U.S. Pat. No. 4,254,062 discloses separation of dichlorotoluene isomers by using a zeolite of the X or Y type, but separation of a 1,3,5-substituted isomer is not taught at all.
U.S. Pat. No. 4,124,770 discloses a process in which xylenol is separated from a mixture of xylenol and cresol by using a zeolite, but separation of a xylenol isomer mixture or cresol isomer mixture is not taught at all.